The convergence of voice, video and data within a variety of multi-function devices and new applications, along with the evolution of high-definition and 3D video, is driving the need for increased high throughput connectivity throughout the home while assuring a high level of reliability and sustained performance.

Home networks are now expected to support applications such as whole-home audio systems, interactive gaming, Smart Grid utilities management and security monitoring. The rise of HDTV, IPTV and multi-room HD DVR services are significantly raising the throughput requirements for home networking.

HOME CONNECTIVITY IS EXPANDINGIn addition, the proliferation of connected devices and methods for accessing and consuming multimedia content within the home is requiring network technologies to both deliver more throughput and provide more adaptability to meet ad hoc configuration needs. For example, streaming services (Netflix, Hulu, Vudu, Amazon Prime, Pandora etc.) and diverse access devices such as iPads and Xbox, are giving users more options for using digital content within the home  and they do not want to be limited as to where and how they use it.

Despite the ongoing drive for convergence of video, voice and data, home networks often leave disconnected islands in the home (dead spots) where digital content is not available without pulling new cabling or hassling with the inherent coverage limitations of wireless networking. In contrast, standards-based powerline for fixed devices and a combination of powerline and Wi-Fi for mobile devices can deliver a truly comprehensive whole-home solution that bridges all of these digital islands into a comprehensive network of interconnected content for access and viewing anywhere, anytime, and on any screen.

An example, HomePlug AV Certified products enable users to easily access streaming services from anywhere there is a power outlet. It also flexibly delivers high speed throughput to all HDTVs, Blu-ray players, DVRs, PCs and game consoles throughout the home. Combined with a hybrid (Wi-Fi + HomePlug) router or range extender, both stationary and mobile devices are readily supported. Using simple and secure setup with push button authentication, HomePlug can easily extend connectivity to that additional TV or game console in another room without running any new wires.

The introduction of HomePlug AV2 is the next major step forward in performance to support higher throughput for whole-home HD / 3D video, interactive gaming and other demanding multimedia applications; while simultaneously providing interoperability with the growing ecosystem of other applications such as Smart Grid and security functions that HomePlug Alliance addresses via its HomePlug Green PHY standard.

HOMEPLUG AV2 TECHNOLOGYThe widely-adopted HomePlug AV standard has now been enhanced to both extend the reach and throughput of the HomePlug AV2 solution. As shown in Figure 2, both HomePlug Green PHY and HomePlug AV2 are fully interoperable with HomePlug AV, while each provides a distinct set of capabilities for addressing different market requirements.Introduced in 2010, HomePlug Green PHY leveraged the HomePlug AV standard to deliver an energy-efficient and cost-effective networking option with optimized throughput for implementing a wide range of applications such as Smart Grid/Energy management, device automation/control, security monitoring, and other latency-tolerant machine-to-machine communications functions. HomePlug GP provides ample throughput for current and future Smart Grid/Energy applications, while offering reduced complexity and much lower power consumption.

Now, with the introduction of HomePlug AV2, the HomePlug AV architecture also has been extended upward to provide two to five times the performance of HomePlug AV. This enables HomePlug AV2 to provide both the throughput and coverage needed to support the escalating requirements of next-generation multimedia applications.HOMEPLUG AV2 BACKWARD COMPATABILITY IS MAINTAINED

DIFFERENT TECHNOLOGY FEATURES OF HOMEPLUG AV VS. HOMEPLUG AV2In addition to the compatibility between HomePlug AV and HomePlug AV2, there are a number of characteristics that differentiate HomePlug AV2 and provide for its higher bandwidth and coverage capabilities. These enhancements are shown in Figure 4 and are described in the following sections.

ADDITIONAL FREQUENCY SPECTRUM

HomePlug AV2 makes use of additional frequency spectrum (30 to 86 MHz) beyond the frequency used for HomePlug AV, which significantly increases HomePlug AV2 throughput for applications such as multiple HD streams. The additional spectrum also improves peak data rates and performance which is essential for achieving high performance over powerline.

HOMEPLUG AV2 PROVIDES "MIMO" CAPACITIES WITH BEAM FORMING

The HomePlug AV2 specification also incorporates Multiple-Input Multiple-Output (MIMO) capabilities with beamforming, which offers the benefit of improved coverage throughout the home; particularly for previously hard to reach outlets. MIMO enables HomePlug AV2 devices to transmit on any two wire pairs within three-wire configurations. Whereas HomePlug AV always transmits on the Line-Neutral pair, HomePlug AV2 can transmit on any two pairs formed by the Line, Neutral or Ground wires (i.e., Line-Neutral, Line-Ground or Neutral-Ground). This allows for significantly improved peak data rates and performance. MIMO uses two independent transmitters and up to four receivers, with beamforming required to maximize the performance on the independent streams. Some regions and some homes do not have the third wire required to implement MIMO however HomePlug AV2 automatically switches to standard SISO operation whenever the third wire is not available.

HIGHLY EFFICIENT PHY LAYER PPDU STRUCTURE

HomePlug AV2 incorporates a high efficiency PPDU (or packet on the wire) structure that enables lower latency and increases network efficiency. The PPDU also improves packet efficiency by lowering overhead, thus exponentially increasing packet efficiency at higher data rates. HomePlug AV2 achieves greater efficiency in the PPDU primarily through the use of a Short Delimiter structure and Delayed Acknowledgements that enable very short response inter-frame spaces.
IMMEDIATE REPEATING

This feature in HomePlug AV2 expands coverage by repeating the signal on paths with better SNR (Signal to Noise Ratio) characteristics. Repeating is accomplished in a single channel access and segments are not stored at the repeater to minimize latency and resource usage. Also no reassembly and segmentation is required at the repeater.

EFFICIENT NOTCHING

HomePlug AV2 increases throughput by allowing devices to minimize the overhead incurred due to mandatory notching requirements. While in HomePlug AV the mechanism (“windowed OFDM”) for creating the PSD notches is fixed and relatively conservative, AV2 devices may gain up to 20% in efficiency if they implement additional techniques to accommodate sharper PSD notches. Such devices gain additional carriers at the band edges and may utilize shorter cyclic extensions, which reduces the duration of the OFDM symbols.

ADDITIONAL PHYSICAL (PHY) LAYER IMPROVEMENTS

HomePlug AV2 also incorporates improved coding schemes in the PHY, which provide robust error correction and better peak data rates, while assisting with performance improvement on good paths at high data rates. The key improvements are higher order modulation (4096-QAM), higher Code Rates (8/9 code rate) and smaller guard intervals.

ENERGY SAVING MODES

Another key innovation is improved energy efficiency when the device is in standby. HomePlug AV2 enables “sleep mode” for various intervals that are multiples of the beacon period in order to reduce power consumption. Using Power Save Modes that are identical to HomePlug Green PHY, the specification enables selectable “Sleep Window” and “Awake Window” durations. For example, a station can have a small “Awake Window” once every N Beacon Periods, an Awake Window for a portion of a Beacon Period or an “Awake Window” that is M Beacon Periods every N Beacon Periods. Management messages are exchanged so other stations can know when each station is Awake and only transmit to them during the Awake periods.